Water-dispersed pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

Abstract

Provided is a water-dispersed pressure-sensitive adhesive composition useful for purposes of producing a pressure-sensitive adhesive sheet having high rough surface adhesiveness also in a good balance with the other properties, and so on. The pressure-sensitive adhesive composition comprises an acrylic polymer pA X , and an acrylic polymer pA Y having a Mw of 1×10 3 to 50×10 3 and a glass transition temperature of −15° C. or below, at a mass ratio of 100:6-35. pA X comprises a C 1-18 alkyl (meth)acrylate M1 X as a primary component. pA Y has a copolymer composition containing, as its constituting monomers, a C 1-18 alkyl(meth)acrylate M1 Y and a functional-group-containing monomer M2 Y . The number of the functional groups derived from the monomer M2 Y contained per 100 g of pA Y is greater than 0 12 mol up to 0.50 mol.

1 . A water-dispersed pressure-sensitive adhesive composition comprising in an aqueous solvent an acrylic polymer pA X  and an acrylic polymer pA Y , wherein:
 the polymer pA X  and the polymer pA Y  have a mass ratio of 100:6 to 100:35;   the polymer pA X  comprises an alkyl(meth)acrylate M1 having an alkyl group with 1 to 18 carbon atoms;   the polymer pA Y  has a weight average molecular weight Mw of 1×10 3  to 50×10 3 ; a glass transition temperature of −15° C. or below; and a copolymer composition containing, as a monomer constituting the polymer pA Y , at least an alkyl(meth)acrylate M 1   Y  having an alkyl group with 1 to 18 carbon atoms and a functional-group-containing monomer M 2   Y ; and   the number of functional groups contained in the polymer pA Y  is greater than 0.12 mol up to 0.50 mol per 100 g of the polymer pA Y , with the functional groups being derived from the monomer M 2   Y .   
     
     
         2 . The water-dispersed pressure-sensitive adhesive composition according to  claim 1 , wherein the monomer M 2   Y  comprises at least one kind of a carboxyl-group-containing monomer. 
     
     
         3 . The water-dispersed pressure-sensitive adhesive composition according to  claim 1 , wherein the monomer M 2   Y  comprises at least either one of acrylic acid and acrylic acid dimer. 
     
     
         4 . The water-dispersed pressure-sensitive adhesive composition according to  claim 1 , wherein the polymer pA X  has a weight average molecular weight for its tetrahydrofuran-soluble portion of 30×10 4  to  100×l 10   4 . 
     
     
         5 . The water-dispersed pressure-sensitive adhesive composition according to  claim 1 , wherein the polymer pA X  has a copolymer composition containing at least 50% by mass of 2-ethylhexyl acrylate and the polymer pA Y  has a copolymer composition containing at least 50% by mass of butyl acrylate. 
     
     
         6 . The water-dispersed pressure-sensitive adhesive composition according to  claim 1 , further comprising 5 to 40 parts by mass of a tackifier relative to 100 parts by mass of the polymer pA X . 
     
     
         7 . The water-dispersed pressure-sensitive adhesive composition according to  claim 6 , wherein the tackifier is a rosin-based resin. 
     
     
         8 . The water-dispersed pressure-sensitive adhesive composition according to  claim 1 , wherein a pressure-sensitive adhesive formed of the water-dispersed pressure-sensitive adhesive composition has a mass fraction for its ethyl-acetate-insoluble portion of 20 to 55%. 
     
     
         9 . A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed of the water-dispersed pressure-sensitive adhesive composition according to  claim 1 .